Lubricating oil composition for refrigerators

ABSTRACT

Provided is a lubricating oil composition for a refrigerator which uses a base oil including as the main component at least one kind of oxygen-containing compounds selected from polyoxyalkylene glycols, polyvinyl ethers, copolymers of poly(oxy)alkylene glycols or monoethers thereof and polyvinyl ethers, polyol esters, and polycarbonates. The lubricating oil composition for a refrigerator is used for a refrigerator that uses, as a refrigerant, a fluorine-containing organic compound, which is a refrigerant applicable to current car air conditioner systems or the like and has a specific polar structure, and has favorable sealing property, a low coefficient of friction factor in a sliding part, and excellent stability as well as excellent compatibility with the refrigerant.

CONTINUATION DATA

This application is a Continuation of U.S. application Ser. No.13/315,845, filed Dec. 9, 2011, now U.S. Pat. No. 8,603,354, which is aContinuation of U.S. application Ser. No. 12/513,235, filed on May 1,2009, abandoned, which is a National Stage of PCT/JP2007/071289 filed onNov. 1, 2009.

TECHNICAL FIELD

The present invention relates to a lubricating oil composition for arefrigerator. More specifically, the present invention relates to alubricating oil composition for a refrigerator using, as a refrigerant,a fluorine-containing organic compound containing a specific polarstructure. The refrigerant has a low global warming potential and isapplicable to, in particular, current car air conditioner systems or thelike. The lubricating oil composition for a refrigerator uses a base oilincluding a specific oxygen-containing compound as a main component.

BACKGROUND ART

In general, a compression refrigerator includes at least a compressor, acondenser, an expansion mechanism (such as an expansion valve), and anevaporator, or further includes a drier, and is structured so that amixed liquid of a refrigerant and lubricating oil (refrigerator oil)circulates in the closed system. In such compression refrigerator, thetemperature in the compressor is generally high, and the temperature inthe condenser is generally low, though such general theory is notapplicable to a certain kind of such compression refrigerator.Accordingly, the refrigerant and the lubricating oil must circulate inthe system without undergoing phase separation in a wide temperaturerange from low temperature to high temperature. In general, therefrigerant and the lubricating oil have regions where they undergophase separation at low temperature and high temperature. Moreover, thehighest temperature of the region where the refrigerant and thelubricating oil undergo phase separation at low temperature ispreferably −10° C. or lower, or particularly preferably −20° C. orlower. On the other hand, the lowest temperature of the region where therefrigerant and the lubricating oil undergo phase separation at hightemperature is preferably 30° C. or higher, or particularly preferably40° C. or higher. The occurrence of the phase separation during theoperation of the refrigerator adversely affects the lifetime orefficiency of the refrigerator to a remarkable extent. For example, whenthe phase separation of the refrigerant and the lubricating oil occursin the compressor portion, a movable part is insufficiently lubricated,with the result that baking or the like occurs to shorten the lifetimeof the refrigerator remarkably. On the other hand, when the phaseseparation occurs in the evaporator, the lubricating oil having a highviscosity is present, with the result that the efficiency of heatexchange reduces.

A chlorofluorocarbon (CFC), a hydrochlorofluorocarbon (HCFC), or thelike has been heretofore mainly used as a refrigerant for arefrigerator. However, such compounds each contain chlorine that isresponsible for environmental issues, so investigation has beenconducted on a chlorine-free alternative refrigerant such as ahydrofluorocarbon (HFC). A hydrofluorocarbon typified by, for example,1,1,1,2-tetrafluoroethane, difluoromethane, pentafluoroethane, or1,1,1-trifluoroethane (hereinafter referred to as “R134a”, “R32”,“R125”, or “R143a”, respectively) has been attracting attention, and,for example, R134a has been used in a car air conditioner system.

However, because the influence of the HFC is also concerned from theviewpoint of the global warming, so-called natural refrigerants such ascarbon dioxide have attracted attention as alternative refrigerantssuitable for environmental protection. The carbon dioxide requires highpressure, and hence cannot be used in the current car air conditionersystem.

A refrigerant having a specific polar structure in the molecules such asan unsaturated fluorinated hydrocarbon compound (see, for example,Patent Document 1), a fluorinated ether compound (see, for example,Patent Document 2), a fluorinated alcohol compound, or a fluorinatedketone compound has been found to be a refrigerant which has a lowglobal warming potential and can be used in a current car airconditioner system.

The lubricating oil for a refrigerator that uses the refrigerant isdemanded to have favorable sealing property, a low coefficient offriction in a sliding part, and excellent stability as well as excellentcompatibility with the refrigerant.

-   Patent Document 1: 2006-503961 A-   Patent Document 2: JP 7-507342 A

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Under the circumstances, an object of the present invention is toprovide a lubricating oil composition for a refrigerator using, as arefrigerant, a fluorine-containing organic compound containing aspecific polar structure. The refrigerant has a low global warmingpotential and is applicable to, in particular, current car airconditioner systems or the like. The lubricating oil composition for arefrigerator has favorable sealing property, a low coefficient offriction in a sliding part, and excellent stability as well as excellentcompatibility with the refrigerant.

Means for Solving the Problems

The inventors of the present invention have studied extensively toachieve the object. As a result, the inventors found that the objectcould be achieved by using a specific oxygen-containing compound as abase oil, and preferably using a specific material for a sliding part ina refrigerator. The present invention has been completed based on thosefindings.

That is, the present invention provides:

(1) a lubricating oil composition for a refrigerator, the refrigeratorusing a refrigerant including at least one kind of fluorine-containingorganic compounds selected from compounds represented by the followingmolecular formula (A) or including a combination of thefluorine-containing organic compound and a saturated fluorinatedhydrocarbon compound,C_(p)O_(q)F_(r)R_(s)  (A)where: R represents Cl, Br, I, or H; p represents an integer of 1 to 6,q represents an integer of 0 to 2, r represents an integer of 1 to 14,and s represents an integer of 0 to 13; and provided that, when qrepresents 0, p represents 2 to 6 and one or more carbon-carbonunsaturated bonds are included in molecules, in which the compositioncomprises a base oil including as a main component at least one kind ofoxygen-containing compounds selected from polyoxyalkylene glycols,polyvinyl ethers, copolymers of poly(oxy)alkylene glycols or monoethersthereof and polyvinyl ethers, polyol esters, and polycarbonates;(2) a lubricating oil composition for a refrigerator, the refrigeratorusing a refrigerant including at least one kind of fluorine-containingorganic compounds selected from a fluorinated ether compound, afluorinated alcohol compound, and a fluorinated ketone compound, orincluding a combination of the fluorine-containing organic compound anda saturated fluorinated hydrocarbon compound, in which the compositioncomprises a base oil including as a main component at least one kind ofoxygen-containing compounds selected from polyoxyalkylene glycols,polyvinyl ethers, copolymers of poly(oxy)alkylene glycols or monoethersthereof and polyvinyl ethers, polyol esters, and polycarbonates;(3) the lubricating oil composition for a refrigerator according to theitem (1) or (2), in which the base oil has a kinematic viscosity of 2 to50 mm²/s at 100° C.;(4) the lubricating oil composition for a refrigerator according to anyone of the items (1) to (3), in which the base oil has a number averagemolecular weight of 500 or more;(5) the lubricating oil composition for a refrigerator according to anyone of the items (1) to (4), in which the base oil has a flash point of150° C. or higher;(6) the refrigerator oil composition for a refrigerator according to anyone of the items (1) to (5), further including at least one kind of anadditive selected from an extreme pressure agent, an oiliness agent, anantioxidant, an acid scavenger, and an anti-foaming agent;(7) the lubricating oil composition for a refrigerator according to anyone of the items (1) to (6), in which the fluorine-containing organiccompound in the refrigerant is a fluorinated dimethyl ether;(8) the lubricating oil composition for a refrigerator according to anyone of the items (1) to (6), in which the fluorine-containing organiccompound in the refrigerant is a fluorinated methyl alcohol;(9) the lubricating oil composition for a refrigerator according to anyone of the items (1) to (6), in which the fluorine-containing organiccompound in the refrigerant is a fluorinated acetone;(10) the lubricating oil composition for a refrigerator according to anyone of the items (1) to (9), in which the saturated fluorinatedhydrocarbon compound in the refrigerant is at least one kind selectedfrom 1,1-difluoroethane, trifluoroethane, tetrafluoroethane, andpentafluoroethane;(11) the lubricating oil composition for a refrigerator according to anyone of the items (1) to (10), in which a sliding part in a refrigeratoris formed of an engineering plastic or includes an organic coating filmor an inorganic coating film;(12) the lubricating oil composition for a refrigerator according to theitem (11), in which the organic coating film is apolytetrafluoroethylene coating film, a polyimide coating film, or apolyamideimide coating film;(13) the lubricating oil composition for a refrigerator according to theitem (11), in which the inorganic coating film is a graphite film, adiamond-like carbon film, a tin film, a chromium film, a nickel film, ora molybdenum film;(14) the lubricating oil composition for a refrigerator according to anyone of the items (1) to (13), which is used in a car air conditioner, anelectrically-driven car air conditioner, a gas heat pump, an airconditioner, a cold storage, various hot-water supply systems for avending machine or a showcase, or a refrigerating and heating system;and(15) the lubricating oil composition for a refrigerator according to theitem (14), in which a water content in a system is 300 mass ppm or lessand a residual air content in the system is 10 kPa or less.

Effect of the Invention

According to the present invention, there can be provided a lubricatingoil composition for a refrigerator using, as a refrigerant, afluorine-containing organic compound containing a specific polarstructure. The refrigerant has a low global warming potential and isapplicable to, in particular, current car air conditioner systems or thelike. The lubricating oil composition for a refrigerator has favorablesealing property, a low coefficient of friction in a sliding part, andexcellent stability as well as excellent compatibility with therefrigerant.

BEST MODE FOR CARRYING OUT THE INVENTION

The lubricating oil composition for a refrigerator of the presentinvention uses a refrigerant including at least one kind offluorine-containing organic compounds selected from compoundsrepresented by the following molecular formula (A) or including acombination of the fluorine-containing organic compound and a saturatedfluorinated hydrocarbon compound,C_(p)O_(q)F_(r)R_(s)  (A)where: R represents Cl, Br, I, or H; p represents an integer of 1 to 6,q represents an integer of 0 to 2, r represents an integer of 1 to 14,and s represents an integer of 0 to 13; and provided that, when qrepresents 0, p represents an integer of 2 to 6 and one or morecarbon-carbon unsaturated bonds are included in molecules.

<Refrigerant>

The molecular formula (A) represents the kind and the number of theelements in the molecules. The formula (A) represents thefluorine-containing organic compound in which p as the number of thecarbon atoms C represents 1 to 6. As long as the fluorine-containingorganic compound is a fluorine-containing organic compound having 1 to 6carbon atoms, the fluorine-containing organic compound can have physicaland chemical properties required for the refrigerant, such as a boilingpoint, a congealing point, and an evaporative latent heat.

In the molecular formula (A), a binding form of p carbon atomsrepresented by C_(p) includes a carbon-carbon single bond, anunsaturated bond such as a carbon-carbon double bond, a carbon-oxygendouble bond, and the like. The carbon-carbon unsaturated bond ispreferably a carbon-carbon double bond from the viewpoint of stability.The number of the carbon-carbon double bond is 1 or more or preferably1.

In addition, in the molecular formula (A), a binding form of q oxygenatoms represented by O_(q) is preferably the oxygen parts of an ethergroup hydroxyl group or carbonyl group. The number of the oxygen atoms qmay be 2, and the case where the compound has two ether groups, hydroxylgroups, or the like is also included.

In addition, in the case where q represents 0 in O_(q) and no oxygenatom is included in the molecules, p represents 2 to 6, and themolecules have one or more unsaturated bonds such as a carbon-carbondouble bond. That is, at least one of binding forms of p carbon atomsrepresented by C_(p) needs to be a carbon-carbon unsaturated bond.

In addition, in the molecular formula (A), R represents Cl, Br, I, or H,and may represent any one of them. R preferably represents H because ofits less possibility of destroying an ozone layer.

As described above, as the fluorine-containing organic compoundrepresented by the molecular formula (A), a fluorinated ether compound,a fluorinated alcohol compound, a fluorinated ketone compound, anunsaturated hydrocarbon compound, and the like are suitably exemplified.

Hereinafter, those compounds are described.

[Fluorinated Ether Compound]

In the present invention, as the fluorinated ether compound used as arefrigerant for a refrigerator, there are exemplified fluorinated ethercompounds where, in the molecular formula (A), R represents H, and prepresents an integer of 2 to 6, q represents an integer of 1 to 2, rrepresents an integer of 1 to 14, and s represents an integer of 0 to13.

Examples of preferred fluorinated ether compound include: a fluorinatedcompound of a chain aliphatic ether having 2 to 6 carbon atoms, 1 or 2ether bonds, and a straight-chain or branched alkyl group; and afluorinated compound of a cyclic aliphatic ether having 3 to 6 carbonatoms and 1 to 2 ether bonds.

Specific examples thereof include dimethyl ethers having 1 to 6 fluorineatoms introduced, methyl ethyl ethers having 1 to 8 fluorine atomsintroduced, dimethoxymethanes having 1 to 8 fluorine atoms introduced,methylpropyl ethers having 1 to 10 fluorine atoms introduced,methylbutyl ethers having 1 to 12 fluorine atoms introduced, ethylpropylethers having 1 to 12 fluorine atoms introduced, oxetanes having 1 to 6fluorine atoms introduced, 1,3-dioxoranes having 1 to 6 fluorine atomsintroduced, and tetrahydrofurans having 1 to 8 fluorine atomsintroduced.

Examples of those fluorinated ether compounds include hexafluorodimethylether, pentafluorodimethyl ether, bis(difluoromethyl)ether, fluoromethyltrifluoromethyl ether, trifluoromethyl methyl ether, perfluorodimethoxymethane, 1-trifluoromethoxy-1,1,2,2-tetrafluoroethane, difluoromethoxypentafluoroethane, 1-trifluoromethoxy-1,2,2,2-tetrafluoroethane,1-difluoromethoxy-1,1,2,2-tetrafluoroethane,1-difluoromethoxy-1,2,2,2-tetrafluoroethane,1-trifluoromethoxy-2,2,2-trifluoroethane,1-difluoromethoxy-2,2,2-trifluoroethane, perfluorooxetane,perfluoro-1,3-dioxolane, various isomers of pentafluorooxetane, andvarious isomers of tetrafluorooxetane.

In the present invention, one kind of the fluorinated ether compoundsmay be used alone or two or more kinds thereof may be used incombination.

[Fluorinated Alcohol Compound]

In the present invention, as the fluorinated alcohol compound used as arefrigerant for a refrigerator and represented by the general formula(A), there are exemplified fluorinated ether compounds where, in themolecular formula (A), R represents H, p represents 1 to 6, q represents0 to 2, r represents 1 to 13, and represents 1 to 13.

Examples of preferred fluorinated alcohol compound include a fluorinatedcompound of a straight-chain or branched aliphatic alcohols each having1 to 6 carbon atoms and 1 or 2 hydroxyl groups.

Specific examples thereof include methyl alcohols having 1 to 3 fluorineatoms introduced, ethyl alcohols having 1 to 5 fluorine atomsintroduced, propyl alcohols having 1 to 7 fluorine atoms introduced,butyl alcohols having 1 to 9 fluorine atoms introduced, pentyl alcoholshaving 1 to 11 fluorine atoms introduced, ethylene glycols having 1 to 4fluorine atoms introduced, and propylene glycols having 1 to 6 fluorineatoms introduced.

Examples of those fluorinated alcohol compounds include monofluoromethylalcohol, difluoromethyl alcohol, trifluoromethyl alcohol, variousisomers of difluoroethyl alcohol, various isomers of trifluoroethylalcohol, various isomers of tetrafluoroethyl alcohol, pentafluoroethylalcohol, various isomers of difluoropropyl alcohol, various isomers oftrifluoropropyl alcohol, various isomers of tetrafluoropropyl alcohol,various isomers of pentafluoropropyl alcohol, various isomers ofhexafluoropropyl alcohol, heptafluoropropyl alcohol, various isomers ofdifluorobutyl alcohol, various isomers of trifluorobutyl alcohol,various isomers of tetrafluorobutyl alcohol, various isomers ofpentafluorobutyl alcohol, various isomers of hexafluorobutyl alcohol,various isomers heptafluorobutyl alcohol, various isomers ofoctafluorobutyl alcohol, nonafluorobutyl alcohol, various isomers ofdifluoroethylene glycol, trifluoroethylene glycol, tetrafluoroethyleneglycol, and various isomers of difluoropropylene glycol, various isomersof trifluoropropylene glycol, various isomers of tetrafluoropropyleneglycol, various isomers of pentafluoropropylene glycol, a fluorinatedpropylene glycol such as hexafluoropropylene glycol, and a fluorinatedtrimethylene glycol corresponting to the fluorinated propylene glycol.

In the present invention, one kind of the fluorinated alcohol compoundsmay be used alone or two or more kinds thereof may be used incombination.

[Fluorinated Ketone Compound]

In the present invention, as the fluorinated ketone compound used as arefrigerant for a refrigerator, there are exemplified fluorinated ketonecompounds in which, in the molecular formula (A), R represents H, and prepresent 2 to 6, q represents 1 to 2, r represents 1 to 12, and srepresents 0 to 11.

Examples of preferred fluorinated ketone compounds include fluorinatedcompounds of aliphatic ketones each having 3 to 6 carbon atoms and astraight-chain or branched alkyl group.

Specific examples thereof include acetones having 1 to 6 fluorine atomsintroduced, methyl ethyl ketones having 1 to 8 fluorine atomsintroduced, diethyl ketones having 1 to 10 fluorine atoms introduced,and methyl propyl ketones having 1 to 10 fluorine atoms introduced.

Examples of those fluorinated ketone compounds includehexafluorodimethyl ketone, pentafluorodimethyl ketone,bis(difluoromethyl)ketone, fluoromethyl trifluoromethyl ketone,trifluoromethyl methyl ketone, perfluoromethyl ethyl ketone,trifluoromethyl-1,1,2,2-tetrafluoroethyl ketone, difluoromethylpentafluoroethyl ketone, trifluoromethyl-1,1,2,2-tetrafluoroethylketone, difluoromethyl-1,1,2,2-tetrafluoroethyl ketone,difluoromethyl-1,2,2,2-tetrafluoroethyl ketone,trifluoromethyl-2,2,2-trifluoroethyl ketone, anddifluoromethyl-2,2,2-trifluoroethyl ketone.

In the present invention, one kind of the fluorinated ketone compoundsmay be used alone or two or more kinds thereof may be used incombination.

[Unsaturated Fluorinated Hydrocarbon Compound]

In the present invention, as the unsaturated fluorinated hydrocarboncompound used as a refrigerant for a refrigerator, there are exemplifiedunsaturated fluorinated hydrocarbon compounds where, in the molecularformula (A), R represents H, and p represents 2 to 6, q represents 0, rrepresents 1 to 12, and s represents 0 to 11.

Examples of preferred unsaturated fluorinated hydrocarbon compoundsinclude a fluorinated compound of a straight-chain or branched chainolefin having 2 to 6 carbon atoms and a fluorinated compound of a cyclicolefin having 4 to 6 carbon atoms.

Specific examples thereof include ethylene having 1 to 3 fluorine atomsintroduced, propene having 1 to 5 fluorine atoms introduced, buteneshaving 1 to 7 fluorine atoms introduced, pentenes having 1 to 9 fluorineatoms introduced, hexenes having 1 to 11 fluorine atoms introduced,cyclobutene having 1 to 5 fluorine atoms introduced, cyclopentene having1 to 7 fluorine atoms introduced, and cyclohexene having 1 to 9 fluorineatoms introduced.

Of those unsaturated fluorinated hydrocarbon compounds, a fluorinatedcompound of propene is preferable and for example, various kinds ofisomers of pentafluoropropene, 3,3,3-trifluoropropene, and1,3,3,3-tetrafluoropropene are suitable.

In the present invention, one kind of the unsaturated fluorinatedhydrocarbon compounds may be used alone or two or more kinds thereof maybe used in combination.

[Saturated Fluorinated Hydrocarbon Compound]

The saturated fluorinated hydrocarbon compound is a refrigerant that canbe mixed, as required, in at least one kind of the fluorine-containingorganic compounds selected from the compounds represented by the generalformula (A).

As the saturated fluorinated hydrocarbon compound, a fluorinatedcompound of alkane having 2 to 4 carbon atoms is preferable andfluorinated compounds of ethane such as 1,1-difluoroethane,1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1,1,1,2-tetrafluoroethane,1,1,2,2-tetrafluoroethane, and 1,1,1,2,2-pentafluoroethane areparticularly suitable. One kind of the saturated fluorinated hydrocarboncompounds may be used alone or two or more kinds thereof may be used incombination.

In addition, the blending amount of the saturated fluorinatedhydrocarbon compound is typically 30 mass % or less, preferably 20 mass% or less, and more preferably 10 mass % or less based on the totalamount of the refrigerant.

The present invention also provides a lubricating oil composition for arefrigerator, which uses a refrigerant including at least one kind of afluorine-containing organic compound selected from the fluorinated ethercompounds, fluorinated alcohol compounds, and fluorinated ketonecompounds, or including a combination of the fluorine-containing organiccompound and the saturated fluorinated hydrocarbon compound.

The lubricating oil composition for a refrigerator of the presentinvention (hereinafter may be referred to as refrigerator oilcomposition) is a lubricating oil composition for a refrigerator whichuses the refrigerant and has a feature of using as a base oil including,as a main component, at least one kind of oxygen-containing compoundsselected from polyoxyalkylene glycols, polyvinyl ethers, copolymers ofpoly(oxy)alkylene glycols or monoethers thereof and polyvinyl ethers,polyolesters, and polycarbonates.

<Base Oil>

[Polyoxyalkylene Glycols]

Examples of the polyoxyalkylene glycols which can be used as the baseoil in the refrigerator oil composition of the present invention includecompounds each represented by the following general formula (I):R¹—[(OR²)_(m)—OR³]_(n)  (I)where R¹ represents a hydrogen atom, an alkyl group having 1 to 10carbon atoms, an acyl group having 2 to 10 carbon atoms, or an aliphatichydrocarbon group having 1 to 10 carbon atoms and 2 to 6 bonding sites,R² represents an alkylene group having 2 to 4 carbon atoms, R³represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms,or an acyl group having 2 to 10 carbon atoms, n represents an integer of1 to 6, and m represents such a number that an average value for m×n is6 to 80.

In the general formula (I), an alkyl group represented by R¹ or R³ maybe straight-chain, branched, or cyclic. Specific examples of the alkylgroup include a methyl group, an ethyl group, an n-propyl group, anisopropyl group, various butyl groups, various pentyl groups, varioushexyl groups, various heptyl groups, various octyl groups, various nonylgroups, various decyl groups, a cyclopentyl group, and a cyclohexylgroup. When the alkyl group has more than 10 carbon atoms, compatibilitywith the refrigerant reduces, so the phase separation of the compoundand the refrigerant may occur. The alkyl group has preferably 1 to 6carbon atoms.

In addition, an alkyl group portion of the acyl group represented by R¹or R³ may be straight-chain, branched, or cyclic. Specific examples ofthe alkyl group portion of the acyl group include various groups eachhaving 1 to 9 carbon atoms described as specific examples of the abovealkyl group. When the acyl group has more than 10 carbon atoms,compatibility with the refrigerant reduces, so the phase separation ofthe compound and the refrigerant may occur. The acyl group haspreferably 2 to 6 carbon atoms.

When R¹ and R³ each represent an alkyl group or an acyl group, R¹ and R³may be identical to or different from each other.

Further, when n represents 2 or more, multiple R³'s in one molecule maybe identical to or different from each other.

When R¹ represents an aliphatic hydrocarbon group having 1 to 10 carbonatoms and 2 to 6 bonding sites, the aliphatic hydrocarbon group may bestraight-chain or cyclic. Examples of the aliphatic hydrocarbon grouphaving 2 bonding sites include an ethylene group, a propylene group, abutylene group, a pentylene group, a hexylene group, a heptylene group,an octylene group, a nonylene group, a decylene group, a cyclopentylenegroup, and a cyclohexylene group. In addition, examples of the aliphatichydrocarbon group having 3 to 6 bonding sites include residues eachobtained by removing a hydroxyl group from a polyhydric alcohol such astrimethylolpropane, glycerin, pentaerythritol, sorbitol,1,2,3-trihydroxycyclohexane, or 1,3,5-trihydroxycyclohexane.

When the aliphatic hydrocarbon group has more than 10 carbon atoms,compatibility with the refrigerant reduces, so the phase separation ofthe compound and the refrigerant may occur. The aliphatic hydrocarbongroup has preferably 2 to 6 carbon atoms.

R² in the general formula (I) represents an alkylene group having 2 to 4carbon atoms, and an oxyalkylene group as a repeating unit is, forexample, anoxyethylene group, an oxypropylene group, or an oxybutylenegroup. Oxyalkylene groups in one molecule of the compound may beidentical to each other, or may be composed of two or more kinds ofoxyalkylene groups; a compound containing at least an oxypropylene unitin any one of its molecules is preferable, and, in particular, acompound containing 50 mol % or more oxypropylene units in theoxyalkylene units is suitable.

n in the general formula (I) represents an integer of 1 to 6, and isdetermined in accordance with the number of bonding sites of R¹. Forexample, when R¹ represents an alkyl group or an acyl group, nrepresents 1, and when R¹ represents an aliphatic hydrocarbon grouphaving 2, 3, 4, 5, or 6 bonding site, n represents 2, 3, 4, 5, or 6,respectively. In addition, m represents such a number that an averagevalue for m×n is 6 to 80. When the average value for m×n deviates fromthe range, the object of the present invention cannot be sufficientlyachieved.

The polyoxyalkylene glycols represented by the general formula (I)includes a polyoxyalkylene glycol having a hydroxyl group at any one ofits terminals, and can be suitably used even when the compound containsthe hydroxyl group as long as the content of the hydroxyl group is 50mol % or less with respect to all terminal groups. A content of thehydroxyl group in excess of 50 mol % is not preferable because themoisture-absorbing property of the compound increases, and the viscosityindex of the compound reduces.

As those polyoxyalkylene glycols, polyoxypropylene glycol dimethyl etherrepresented by the following general formula,

where x represents a number of 6 to 80, polyoxyethylene polyoxypropyleneglycol dimethyl ether represented by the following general formula,

where a and b each represent 1 or more and a number so that a total of aand b is 6 to 80, polyoxypropylene glycol monobutyl ether represented bythe following general formula,

where x represents a number of 6 to 80, and polyoxypropylene glycoldiacetate are suitable from the viewpoints of economical efficiency andeffects.

It should be noted that anyone of those detailed in JP 02-305893 A canbe used as the polyoxyalkylene glycols represented by the above generalformula (I).

In the present invention, one kind of those polyoxyalkylene glycols maybe used alone, or two or more kinds thereof may be used in combination.

[Polyvinyl Ethers]

In the refrigerator oil composition of the present invention, thepolyvinyl ethers that can be used as base oils are each a compoundincluding, as a main component, a polyvinyl-based compound having aconstitutional unit represented by the following general formula (II).

In the general formula (II), R⁴, R⁵, and R⁶ each represent a hydrogenatom or a hydrocarbon group having 1 to 8 carbon atoms and may beidentical to or different from one another.

The hydrocarbon group herein specifically refers to: alkyl groups suchas a methyl group, an ethyl group, an n-propyl group, an isopropylgroup, an n-butyl group, an isobutyl group, a sec-butyl group, atert-butyl group, various pentyl groups, various hexyl groups, variousheptyl groups, and various octyl groups; cycloalkyl groups such as acyclopentyl group, a cyclohexyl group, various methyl cyclohexyl groups,various ethyl cyclohexyl groups, and various dimethyl cyclohexyl groups;aryl groups such as a phenyl group, various methyl phenyl groups,various ethyl phenyl groups, and various dimethyl phenyl groups; andaryl alkyl groups such as a benzyl group, various phenyl ethyl groups,and various methyl benzyl groups. It should be noted that those R⁴, R⁵,and R⁶ each particularly preferably represent a hydrogen atom or ahydrocarbon group having 3 or less carbon atoms.

On the other hand, R⁷ in the general formula (II) represent a divalenthydrocarbon group having 2 to 10 carbon atoms. Specific examples of thedivalent hydrocarbon group having 2 to 10 carbon atoms herein include: adivalent aliphatic group such as an ethylene group, a phenyl ethylenegroup, a 1,2-propylene group, a 2-phenyl-1,2-propylene group, a1,3-propylene group, various butylene groups, various pentylene groups,various hexylene groups, various heptylene groups, various octylenegroups, various nonylene groups, and various decylene groups; alicyclicgroups in which alicyclic hydrocarbon has two bonding sites, such ascyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane,and propylcyclohexane; divalent aromatic hydrocarbon groups such asvarious phenylene groups, various methylphenylene groups, variousethylphenylene groups, various dimethylphenylene groups, and variousnaphthylenes; alkyl aromatic groups having monovalent bonding sites ineach of the alkyl group portion and the aromatic portion of the alkylaromatic hydrocarbon, such as toluene, xylene, and ethyl benzene; andalkyl aromatic groups each having a bonding site in the alkyl groupportion of a polyalkyl aromatic hydrocarbon such as xylene anddiethylbenzene. Of those, aliphatic groups having 2 to 4 carbon atomsare particularly preferable. In addition, multiple R⁷O's are identicalto or different from one another.

It should be noted that pin the general formula (II) represents thenumber of the repeating and such a number that average value thereof isin the range of 0 to 10 or preferably 0 to 5.

In addition, R⁸ in the general formula (II) represents a hydrocarbongroup having 1 to 10 carbon atoms. The hydrocarbon group hereinspecifically refers to: alkyl groups such as a methyl group, an ethylgroup, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, a sec-butyl group, a tert-butyl group, various pentylgroups, various hexyl groups, various heptyl groups, various octylgroups, various nonyl groups, and various decyl groups; cycloalkylgroups such as a cyclopentyl group, a cyclohexyl group, various methylcyclohexyl groups, various ethyl cyclohexyl groups, various propylcyclohexyl groups, and various dimethyl cyclohexyl groups; aryl groupssuch as a phenyl group, various methyl phenyl groups, various ethylphenyl groups, various dimethyl phenyl groups, various propyl phenylgroups, various trimethyl phenyl groups, various butyl phenyl groups,and various naphthyl groups; and aryl alkyl groups such as a benzylgroup, various phenyl ethyl groups, various methyl benzyl groups,various phenyl propyl groups, and various phenyl butyl groups. Of those,a hydrocarbon group having 8 or less carbon atoms is preferable. When prepresents 0, an alkyl group having 1 to 6 carbon atoms is preferable,and when p represents 1 or more, an alkyl group having 1 to 4 carbonatoms is particularly preferable.

The polyvinyl ether-based compound in the present invention has aconstitutional unit represented by the general formula (II). The numberof the repeating thereof (that is, polymerization degree) may beappropriately selected according to a desired kinematic viscosity and istypically 2 to 50 mm²/s (100° C.) or preferably 3 to 40 mm²/s (100° C.)

The polyvinyl ether-based compound in the present invention can beproduced by polymerization of the corresponding vinyl ether-basedmonomer. The vinyl ether-based monomer that can be used herein isrepresented by the following general formula (III),

where R⁴, R⁵, R⁶, R⁷, and R⁸, and p each have the same meaning as thatdescribed above. As the vinyl ether-based monomer, there are variouscompounds corresponding to the polyvinyl ether-based compound. Examplesthereof include: vinyl methyl ether, vinyl ethyl ether, vinyl-n-propylether, vinyl-isopropyl ether, vinyl-n-butyl ether, vinyl-isobutyl ether,vinyl-sec-butyl ether, vinyl-tert-butyl ether, vinyl-n-pentyl ether,vinyl-n-hexylether, vinyl-2-methoxyethyl ether, vinyl-2-ethoxyethylether, vinyl-2-methoxy-1-methylethylether, vinyl-2-methoxy-propylether,vinyl-3,6-dioxaheptyl ether, vinyl-3,6,9-trioxadecyl ether,vinyl-1,4-dimethyl-3,6-dioxaheptyl ether,vinyl-1,4,7-trimethyl-3,6,9-trioxadecyl ether, vinyl-2,6-dioxa-4-heptylether, and vinyl-2,6,9-trioxa-4-decyl ether; 1-methoxypropene,1-ethoxypropene, 1-n-propoxypropene, 1-isopropoxypropene,1-n-butoxypropene, 1-isobutoxypropene, 1-sec-butoxypropene,1-tert-butoxypropene, 2-methoxypropene, 2-ethoxypropene,2-n-propoxypropene, 2-isopropoxypropene, 2-n-butoxypropene,2-isobutoxypropene, 2-sec-butoxypropene, and 2-tert-butoxypropene;1-methoxy-1-butene, 1-ethoxy-1-butene, 1-n-propoxy-1-butene,1-isopropoxy-1-butene, 1-n-butoxy-1-butene, 1-isobutoxy-1-butene,1-sec-butoxy-1-butene, 1-tert-butoxy-1-butene, 2-methoxy-1-butene,2-ethoxy-1-butene, 2-n-propoxy-1-butene, 2-isopropoxy-1-butene,2-n-butoxy-1-butene, 2-isobutoxy-1-butene, 2-sec-butoxy-1-butene,2-tert-butoxy-1-butene, 2-methoxy-2-butene, 2-ethoxy-2-butene,2-n-propoxy-2-butene, 2-isopropoxy-2-butene, 2-n-butoxy-2-butene,2-isobutoxy-2-butene, 2-sec-butoxy-2-butene, and 2-tert-butoxy-2-butene.Those vinyl ether-based monomers can be produced by any known methods.

The terminals of the polyvinyl ether-based compound having theconstitutional unit represented by the general formula (II) used as amain component of the refrigerator oil composition of the presentinvention can be converted to a desired structure by a method in thisapplication and a known method. As a converted group, a saturatedhydrocarbon, an ether, an alcohol, a ketone, an amide, and a nitrile areexemplified.

As the polyvinyl ether-based compound used in the base oil in therefrigerator oil composition of the present invention, a compound havingthe following terminal structure is suitable.

That is, the polyvinyl ether-based compound has:

(1) a structure in which one of the terminals is represented by thefollowing general formula (IV),

where R⁹, R¹⁰, and R¹¹ each represent a hydrogen atom, or a hydrocarbongroup having 1 to 8 carbon atoms and may be identical to or differentfrom one another, R¹² represents a divalent hydrocarbon group having 2to 10 carbon atoms, R¹³ represents a hydrocarbon group having 1 to 10carbon atoms, q represents such a number that an average value thereofis 0 to 10, and in the case where multiple R¹²O's are present, multipleR¹²O's may be identical to or different from one another, and

the other terminal is represented by the following general formula (V),

where R¹⁴, R¹⁵, and R¹⁶ each represent a hydrogen atom, or a hydrocarbongroup having 1 to 8 carbon atoms and may be identical to or differentfrom one another, R¹⁷ represents a divalent hydrocarbon group having 2to 10 carbon atoms, R¹⁸ represents a hydrocarbon group having 1 to 10carbon atoms, r represents such a number that an average value thereofis 0 to 10, and when multiple R¹⁷O's are present, multiple R¹⁷O's may beidentical to or different from one another;

(2) a structure in which one of the terminals is represented by thegeneral formula (IV) and the other terminal is represented by thefollowing general formula (VI),

where R¹⁹, R²⁰, and R²¹ each represent a hydrogen atom, or a hydrocarbongroup having 1 to 8 carbon atoms and may be identical to or differentfrom one another, R²² and R²⁴ each represent a divalent hydrocarbongroup having 2 to 10 carbon atoms and may be identical to or differentfrom each other, R²³ and R²⁵ each represent a hydrocarbon group having 1to 10 carbon atoms and may be identical to or different from each other,s and t each represent such a number that an average value thereof is 0to 10 and my be identical to or different from each other, when multipleR²²O's are present, multiple R²²O's may be identical to or differentfrom one another, and when multiple R²⁴O's are present, multiple R²⁴O'smay be identical to or different from one another;

(3) a structure in which one of the terminals is represented by thegeneral formula (IV) and the other terminal is an olefinic, unsaturatedbond; or

(4) a structure in which one of the terminals is represented by thegeneral formula (IV) and the other terminal is represented by thefollowing general formula (VII),

where R²⁶, R²⁷, and R²⁸ each represent a hydrogen atom, or a hydrocarbongroup having 1 to 8 carbon atoms and may be identical to or differentfrom one another.

The polyvinyl ether-based mixture may be a mixture including two or morekinds of the polyvinyl ether-based compounds selected from those havingthe terminal structures in the items (1) to (4). As the mixture, forexample, a mixture of the compounds in the items (1) and (4) and amixture of the compounds in the items (2) and (3) are preferablyexemplified.

Because the kinematic viscosity of the refrigerator oil compositionbefore being mixed in the refrigerant is preferably 2 to 50 mm²/s at100° C., it is preferable to select the raw material, the initiator, andthe reaction condition in such a manner to produce a polyvinylether-based compound having the viscosity in the range as the polyvinylether-based compound. In addition, the number average molecular weightof the polymer is typically 500 or more or preferably 600 to 3,000. Itshould be noted that even the polymer having the kinematic viscosity outof the above range can be adjusted to have the kinematic viscosity inthe range by mixing with a polymer having another kinematic viscosity.

In the present invention, one kind of the polyvinyl ether-basedcompounds may be used alone or two or more kinds thereof may be used incombination.

[Copolymer of Poly(Oxy)Alkylene Glycol or Monoether Thereof andPolyvinyl Ether]

It should be noted that the poly(oxy)alkylene glycol refers to bothpolyalkylene glycol and polyoxyalkylene glycol.

In the refrigerator oil composition of the present invention, as acopolymer of poly(oxy)alkylene glycol or a monoether thereof andpolyvinyl ether that can be used as a base oil, copolymers representedby the following general formula (VIII) and the following generalformula (IX) (hereinafter, referred to as polyvinyl ether-basedcopolymer I and polyvinyl ether-based copolymer II, respectively) areexemplified.

In the general formula (VIII), R²⁹, R³⁰, and R³¹ each represent ahydrogen atom, or a hydrocarbon group having 1 to 8 carbon atoms and maybe identical to or different from one another, R³³ represents a divalenthydrocarbon group having 2 to 4 carbon atoms, R³⁴ represents analiphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, anaromatic group that may have a substituent having 1 to 20 carbon atoms,an acyl group having 2 to 20 carbon atoms, or an oxygen-containinghydrocarbon group having 2 to 50 carbon atoms, R³² represents ahydrocarbon group having 1 to 10 carbon atoms, and when multiple R³⁴'s,R³³'s, and R³²'s are present, multiple R³⁴'s, R³³'s, and R³²'s may beidentical to or different from one another.

Here, specific examples of the hydrocarbon group having 1 to 8 carbonatoms represented by any one of R²⁹ to R³¹ include: alkyl groups such asa methyl group, an ethyl group, an n-propyl group, an isopropyl group,an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butylgroup, various pentyl groups, various hexyl groups, various heptylgroups, and various octyl groups; aryl groups such as a cyclopentylgroup, a cyclohexyl group, various methyl cyclohexyl groups, variousethyl cyclohexyl groups, various dimethyl cyclohexyl groups, and variousdimethyl phenyl groups; and aryl alkyl groups such as a benzyl group,various phenyl ethyl groups, and various methyl benzyl groups. It shouldbe noted that R²⁹, R³⁰, and R³¹ each particularly preferably represent ahydrogen atom.

On the other hand, specific examples of the divalent hydrocarbon grouphaving 2 to 4 carbon atoms represented by R³³ include divalent alkylenegroups such as a methylene group, an ethylene group, a propylene group,a trimethylene group, and various butylene groups.

It should be noted that v in the general formula (VIII) represents thenumber of the repeating of R³³O and represents such a number that anaverage value thereof is in the range of 1 to 50, preferably 1 to 20,more preferably 1 to 10, or particularly preferably 1 to 5. Whenmultiple R³³O's are present, multiple R³³O's are identical to ordifferent from one another.

In addition, k represents a number of 1 to 50, preferably 1 to 10, morepreferably 1 to 2, or particularly preferably 1, and u presents a numberof 0 to 50, preferably 2 to 25, and more preferably 5 to 15. Whenmultiple k's and u's are present, the polymer may be a block polymer ora random polymer.

Further, R³⁴ in the general formula (VIII) preferably represents analkyl group having 1 to 10 carbon atoms, an acyl group having 2 to 10carbon atoms, or an oxygen-containing hydrocarbon group having 2 to 50carbon atoms.

Specific examples of the alkyl group having 1 to 10 carbon atoms includea methyl group, an ethyl group, an n-propyl group, an isopropyl group,an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butylgroup, various pentyl groups, various hexyl groups, various heptylgroups, various octyl groups, various nonyl groups, various decylgroups, a cyclopentyl group, a cyclohexyl group, various methylcyclohexyl groups, various ethyl cyclohexyl groups, various propylcyclohexyl groups, and various dimethyl cyclohexyl groups.

In addition, as the acyl group having 2 to 10 carbon atoms, an acetylgroup, a propionyl group, a butyryl group, an isobutyryl group, avaleryl group, an isovaleryl group, a pivaloyl group, a benzoyl group,and a toluoyl group are exemplified.

Further, specific examples of the oxygen-containing hydrocarbon grouphaving 2 to 50 carbon atoms preferably include a methoxymethyl group, amethoxyethyl group, a methoxypropyl group, a 1,1-bismethoxypropyl group,a 1,2-bismethoxypropyl group, an ethoxypropyl group, a(2-methoxyethoxy)propyl group, and a (1-methyl-2-methoxy)propyl group.

In the general formula (VIII), specific examples of the hydrocarbongroup having 1 to 10 carbon atoms represented by R³² include: alkylgroups such as a methyl group, an ethyl group, an n-propyl group, anisopropyl group, an n-butyl group, an isobutyl group, various pentylgroups, various hexyl groups, various heptyl groups, various octylgroups, various nonyl groups, and various decyl groups; cycloalkylgroups such as a cyclopentyl group, a cyclohexyl group, various methylcyclohexyl groups, various ethyl cyclohexyl groups, various propylcyclohexyl groups, and various dimethyl cyclohexyl groups; aryl groupssuch as a phenyl group, various methyl phenyl groups, various ethylphenyl groups, various dimethyl phenyl groups, various propyl phenylgroups, various trimethyl phenyl groups, various butyl phenyl groups,and various naphthyl groups; and aryl alkyl groups such as a benzylgroup, various phenyl ethyl groups, various methyl benzyl groups,various phenyl propyl groups, and various phenyl butyl groups.

It should be noted that R²⁹ to R³¹, R³⁴, R³³, and v, and R²⁹ to R³² maybe identical to or different from one another among constitutionalunits.

The polyvinyl ether-based copolymer I having the constitutional unitrepresented by the general formula (VIII) has an effect of improving thelubricity, insulating property, and moisture-absorbing property whilesatisfying the compatibility because the polyvinyl ether-based copolymerI is a copolymer. In this case, those properties of the lubricant can beadjusted to the intended level by selecting the kind of the monomer as araw material, the kind of the initiator, and the rate in the copolymer.Therefore, the polyvinyl ether-based copolymer I has an effect that alubricant depending on requirements of the type of a compressor in arefrigerating system or a conditioner system, and the lubricity, thecompatibility, and the like, which are different according to thematerial of a lubricating part, refrigerating capacity, the kind of therefrigerant, and the like, can be obtained freely.

On the other hand, in the polyvinyl ether-based copolymer II representedby the general formula (IX), R²⁹ to R³², R³³, and v each have the samemeaning as that described above. When multiple R³³'s and R³²'s arepresent, each of R³³'s and R³²'s may be identical to or different fromone another. x and y each represent a number of 1 to 50. When multiplex's and y's are present, the polymer may be a block polymer or a randompolymer. X and Y each independently represent a hydrogen atom, ahydroxyl group, or a hydrocarbon group having 1 to 20 carbon atoms.

A production method for the polyvinyl ether-based copolymer Irepresented by the general formula (VIII) is not particularly limited aslong as the polyvinyl ether-based copolymer I can be obtained. Forexample, the polyvinyl ether-based copolymer I can be produced by thefollowing production methods 1 to 3.

(Production Method 1 for Polyvinyl Ether-Based Copolymer I)

In the production method 1, a poly(oxy)alkyleneglycol compoundrepresented by the following general formula (X),R³⁴—(OR³³)_(v)—OH  (X)where R³³ and R³⁴, and v each have the same meaning as that describedabove, is used as an initiator, and a vinyl ether-based compoundrepresented by the following general formula (XI),

where R²⁹ to R³² each have the same meaning as that described above, ispolymerized, whereby the polyvinyl ether-based copolymer I can beobtained.

Examples of poly(oxy)alkylene glycol compound represented by the generalformula (X) include (oxy)alkylene glycol monoethers such as ethyleneglycol monomethylether, diethylene glycol monomethylether, triethyleneglycol monomethylether, propylene glycol monomethylether, dipropyleneglycol monomethylether, and tripropylene glycol monomethylether.

Examples of the vinyl ether-based compounds represented by the generalformula (XI) include: vinyl ethers such as vinyl methyl ether, vinylethyl ether, vinyl-n-propyl ether, vinyl-isopropyl ether, vinyl-n-butylether, vinyl-isobutyl ether, vinyl-sec-butyl ether, vinyl-tert-butylether, vinyl-n-pentyl ether, and vinyl-n-hexyl ether; propenes such as1-methoxypropene, 1-ethoxypropene, 1-n-propoxypropene,1-isopropoxypropene, 1-n-butoxypropene, 1-isobutoxypropene,1-sec-butoxypropene, 1-tert-butoxypropene, 2-methoxypropene,2-ethoxypropene, 2-n-propoxypropene, 2-isopropoxypropene,2-n-butoxypropene, 2-isobutoxypropene, 2-sec-butoxypropene, and2-tert-butoxypropene; and butenes such as 1-methoxy-1-butene,1-ethoxy-1-butene, 1-n-propoxy-1-butene, 1-isopropoxy-1-butene,1-n-butoxy-1-butene, 1-isobutoxy-1-butene, 1-sec-butoxy-1-butene,1-tert-butoxy-1-butene, 2-methoxy-1-butene, 2-ethoxy-1-butene,2-n-propoxy-1-butene, 2-isopropoxy-1-butene, 2-n-butoxy-1-butene,2-isobutoxy-1-butene, 2-sec-butoxy-1-butene, 2-tert-butoxy-1-butene,2-methoxy-2-butene, 2-ethoxy-2-butene, 2-n-propoxy-2-butene,2-isopropoxy-2-butene, 2-n-butoxy-2-butene, and 2-tert-butoxy-2-butene.Those vinyl ether-based monomers can be produced by any known methods.

(Production Method 2 for Polyvinyl Ether-Based Copolymer I)

In the production method 2, an acetal compound represented by thefollowing general formula (XII),

where R²⁹ to R³⁴, and v each have the same meaning as that describedabove, is used as an initiator, and the vinyl ether-based compoundrepresented by the general formula (XI) is polymerized, whereby thepolyvinyl ether-based copolymer I can be obtained.

Examples of the acetal compound represented by the general formula (XII)include acetaldehyde methyl(2-methoxyethyl)acetal, acetaldehydeethyl(2-methoxyethyl)acetal, acetaldehydemethyl(2-methoxy-1-methylethyl)acetal, acetaldehydeethyl(2-methoxy-1-methylethyl)acetal, acetaldehydemethyl[2-(2-methoxyethoxy)ethyl]acetal, acetaldehydeethyl[2-(2-methoxyethoxy)ethyl]acetal, acetaldehydemethyl[2-(2-methoxyethoxy)-1-methylethyl]acetal, and acetaldehydeethyl[2-(2-methoxyethoxy)-1-methylethyl]acetal.

In addition, the acetal compound represented by the general formula(XII) can be produced by reacting one molecule of the poly(oxy)alkyleneglycol compound represented by the general formula (X) with one moleculeof the vinyl ether-based compound represented by the general formula(XI). The obtained acetal compound is used as an initiator after beingisolated or as it is.

(Production Method 3 for Polyvinyl Ether-Based Copolymer I)

In the production method 3, an acetal compound represented by thefollowing general formula (XIII),

where R²⁹ to R³¹, R³³, R³⁴ and v each have the same meaning as thatdescribed above, is used as an initiator, and the vinyl ether-basedcompound represented by the general formula (XI) is polymerized, wherebythe polyvinyl ether-based copolymer I can be obtained.

Examples of the acetal compound represented by the general formula(XIII) include acetaldehyde di(2-methoxyethyl)acetal, acetaldehydedi(2-methoxy-1-methylethyl)acetal, acetaldehydedi[2-(2-methoxyethoxy)ethyl]acetal, and acetaldehydedi[2-(2-methoxyethoxy)-1-methylethyl]acetal.

In addition, the acetal compound represented by the general formula(XIII) can be produced by reacting one molecule of the poly(oxy)alkyleneglycol compound represented by the general formula (X) with one moleculeof a vinyl ether-based compound represented by the following generalformula (XIV),

where R²⁹ to R³¹, R³³, R³⁴, and v each have the same meaning as thatdescribed above. The obtained acetal compound may be used as aninitiator after being isolated or as it is.

The vinyl ether-based copolymer I represented by the general formula(VIII) is a vinyl ether-based copolymer I having a structure in whichone of the terminals is represented by the following formula (XV) or(XVI),

where R²⁹ to R³⁴, and v each have the same meaning as that describedabove, and the other terminal is represented by the following generalformula (XVII) or the following general formula (XVIII),

where R²⁹ to R³⁴, and v each have the same meaning as that describedabove.

Of those polyvinyl ether-based copolymers 1, the following areparticularly suitable for the base oil in the refrigerator oilcomposition of the present invention:

(1) a substance having a structure in which one of the terminal isrepresented by the general formula (XV) or (XVI), and the other terminalis represented by the general formula (XVII) or (XVIII), and in thegeneral formula (VIII), all R²⁹, R³⁰, and R³¹ represent hydrogen atoms,v represents a number of 1 to 4, R³³ represents a divalent hydrocarbongroup having 2 to 4 carbon atoms, R³⁴ represents an alkyl group having 1to 10 carbon atoms, and R³² represents a hydrocarbon group having 1 to10 carbon atoms;(2) a substance having a structure in which one of the terminal isrepresented by the general formula (XV), and the other terminal isrepresented by the general formula (XVIII), and in the general formula(VIII), all R²⁹, R³⁰, and R³¹ represent hydrogen atoms, v represents anumber of 1 to 4, R³³ represents a divalent hydrocarbon group having 2to 4 carbon atoms, R³⁴ represents an alkyl group having 1 to 10 carbonatoms, and R³² represents a hydrocarbon group having 1 to 10 carbonatoms; and(3) a substance having a structure in which one of the terminal isrepresented by the general formula (XVI), and the other terminal isrepresented by the general formula (XVII), and in the general formula(VIII), all R²⁹, R³⁰, and R³¹ represent hydrogen atoms, v represents anumber of 1 to 4, R³³ represents a divalent hydrocarbon group having 2to 4 carbon atoms, R³⁴ represents an alkyl group having 1 to 10 carbonatoms, and R³² represents a hydrocarbon group having 1 to 10 carbonatoms.

On the other hand, a production method for the polyvinyl ether-basedcopolymer II represented by the general formula (IX) is not particularlylimited as long as the polyvinyl ether-based copolymer II can beobtained, and the polyvinyl ether-based copolymer II can be producedefficiently by the following method.

(Production Method for Polyvinyl Ether-Based Copolymer II)

The polyvinyl ether-based copolymer II represented by the generalformula (IX) can be obtained by using poly(oxy)alkylene glycolrepresented by the following general formula (XIX) as a initiator,HO—(R³³O)_(v)—H  (XIX)where R³³ and v each have the same meaning as that described above, andpolymerizing the vinyl ether compound represented by the general formula(XI).

Examples of the poly(oxy)alkylene glycol represented by the generalformula (XIX) include ethylene glycol, diethylene glycol, triethyleneglycol, polyethylene glycol, propylene glycol, dipropylene glycol, andpolypropylene glycol.

In the present invention, one kind of the copolymers of thepoly(oxy)alkylene glycols or monoether thereof and polyvinyl ethers maybe used or two or more kinds thereof may be used in combination.

[Polyol Esters]

An ester of a diol or a polyol having about 3 to 20 hydroxyl groups andan aliphatic acid having about 1 to 24 carbon atoms is preferably usedas the polyol esters to be used as the base oil in the refrigerator oilcomposition of the present invention. Here, examples of the diol includeethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol,1,2-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentylglycol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol,1,7-heptanediol, 2-methyl-2-propyl-1,3-propanediol,2,2-diethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol,1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol. Examples ofthe polyol include: polyhydric alcohols such as trimethylolethane,trimethylolpropane, trimethylolbutane, di-(trimethylolpropane),tri-(trimethylolpropane), pentaerythritol, di-(pentaerythritol),tri-(pentaerythritol), glycerin, polyglycerin (composed of 2 to 20glycerin molecules), 1,3,5-pentanetriol, sorbitol, sorbitan, a sorbitolglycerin condensate, adonitol, arabitol, xylitol, and mannitol; andsaccharides such as xylose, arabinose, ribose, rhamnose, glucose,fructose, galactose, mannose, sorbose, cellobiose, maltose, isomaltose,trehalose, sucrose, raffinose, gentianose, and merenditose, andpartially etherified products and methyl glucosides of the saccharides.Of those, a hindered alcohol such as neopentyl glycol,trimethylolethane, trimethylolpropane, trimethylolbutane,di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol,di-(pentaerythritol), or tri-(pentaerythritol) is preferred as a polyol.

The aliphatic acid may have any number of carbon atoms without anyparticular limitation; an aliphatic acid having 1 to 24 carbon atoms istypically used. Of the aliphatic acids each having 1 to 24 carbon atoms,an aliphatic acid having 3 or more carbon atoms is preferred, analiphatic acid having 4 or more carbon atoms is more preferred, analiphatic acid having 5 or more carbon atoms is still more preferred,and an aliphatic acid having 10 or more carbon atoms is most preferredin terms of lubricity. In addition, an aliphatic acid having 18 or lesscarbon atoms is preferred, an aliphatic acid having 12 or less carbonatoms is more preferred, and an aliphatic acid having 9 or less carbonatoms is still more preferred in terms of compatibility with therefrigerant.

In addition, the aliphatic acid may be a straight-chain aliphatic acidor a branched aliphatic acid; the aliphatic acid is preferably astraight-chain aliphatic acid in terms of lubricity, or is preferably abranched aliphatic acid in terms of hydrolytic stability. Further, thealiphatic acid may be a saturated aliphatic acid or an unsaturatedaliphatic acid.

Examples of the aliphatic acid include: straight-chain or branchedpentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoicacid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid,tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoicacid, octadecanoic acid, nonadecanoic acid, icosanoic acid, and oleicacid; or a neoic acid of which the α-carbon atom is quaternary. Morespecifically, valeric(n-pentanoic) acid, caproic(n-hexanoic) acid,enanthic(n-heptanoic) acid, caprylic(n-ocatanoic) acid,pelargoic(n-nonanoic) acid, capric(n-decanoic) acid,oleic(cis-9-octadecenoic) acid, isopentanoic(3-methylbutanoic) acid,2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and3,5,5-trimethylhexanoic acid are preferred.

It should be noted that the polyol ester may be a partial ester in whichsome of the hydroxyl groups of a polyol remain without being esterified,may be a complete ester in which all of the hydroxyl groups of thepolyol are esterified, or may be a mixture of a partial ester and acomplete ester; the polyol ester is preferably a complete ester.

Of the polyol esters, an ester of a hindered alcohol such as neopentylglycol, trimethylolethane, trimethylolpropane, trimethylolbutane,di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol,di-(pentaerythritol), or tri-(pentaerythritol) is more preferred, and anester of neopentyl glycol, trimethylolethane, trimethylolpropane,trimethylolbutane, or pentaerythritol is still more preferred becausesuch ester is additionally excellent in hydrolytic stability. An esterof pentaerythritol is most preferred because the ester is particularlyexcellent in compatibility with the refrigerant and hydrolyticstability.

Specific examples of the preferred polyol ester include: a diesterformed of neopentyl glycol and one kind or two or more kinds ofaliphatic acids selected from valeric acid, caproic acid, enanthic acid,caprylic acid, pelargoic acid, capric acid, oleic acid, isopentanoicacid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoicacid, and 3,5,5-trimethylhexanoic acid; a triester formed of trimethylolethane and one kind or two or more kinds of aliphatic acids selectedfrom valeric acid, caproic acid, enanthic acid, caprylic acid, pelargoicacid, capric acid, oleic acid, isopentanoic acid, 2-methylhexanoic acid,2-ethylpentanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoicacid; a triester formed of trimethylol propane and one kind or two ormore kinds of aliphatic acids selected from valeric acid, caproic acid,enanthic acid, caprylic acid, pelargoic acid, capric acid, oleic acid,isopentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid,2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid; a triesterformed of trimethylol butane and one kind or two or more kinds ofaliphatic acids selected from valeric acid, caproic acid, enanthic acid,caprylic acid, pelargoic acid, capric acid, oleic acid, isopentanoicacid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoicacid, and 3,5,5-trimethylhexanoic acid; a tetraester formed ofpentaerythritol and one kind or two or more kinds of aliphatic acidsselected from valeric acid, caproic acid, enanthic acid, caprylic acid,pelargoic acid, capric acid, oleic acid, isopentanoic acid,2-methylhexanoic acid, 2-ethylpentanoic acid, 2-ethylhexanoic acid, and3,5,5-trimethylhexanoic acid.

It should be noted that the esters with two or more kinds of aliphaticacids may be a mixture of two or more kinds of esters formed of one kindof aliphatic acid and a polyol. An ester formed of two or more kinds ofmixed aliphatic acids and a polyol, particularly an ester formed ofmixed aliphatic acids and a polyol is excellent in low temperatureproperties and compatibility with a refrigerant.

[Polycarbonates]

The polycarbonates which can be used as the base oil in the refrigeratoroil composition of the present invention is preferably, for example, atleast one kind selected from polycarbonates each having two or morecarbonate bonds in any one of its molecules, that is: compounds eachrepresented by the following general formula (XX),

where: Z represents a residue obtained by removing a hydroxyl group froman e-valent alcohol having 1 to 12 carbon atoms; R³⁵ represents astraight-chain or branched alkylene group having 2 to 10 carbon atoms;R³⁶ represents a monovalent hydrocarbon group having 1 to 12 carbonatoms or a group containing an ether bond represented by R³⁸(O—R³⁷)_(f)—where R³⁸ represents a hydrogen atom or a monovalent hydrocarbon grouphaving 1 to 12 carbon atoms, R³⁷ represents a straight-chain or branchedalkylene group having 2 to 10 carbon atoms, and f represents an integerof 1 to 20; c represents an integer of 1 to 30, d represents an integerof 1 to 50; and e represents an integer of 1 to 6; and (ii) compoundseach represented by the following general formula (XXI),

where: R³⁹ represents a straight-chain or branched alkylene group having2 to 10 carbon atoms; g represents an integer of 1 to 20; and Z, R³⁵,R³⁶, c, d, and e each have the same meaning as that described above.

In each of the general formulae (XX) and (XXI), Z, which represents aresidue obtained by removing a hydroxyl group from a monovalent tohexavalent alcohol having 1 to 12 carbon atoms, particularly preferablyrepresents a residue obtained by removing a hydroxyl group from amonovalent alcohol having 1 to 12 carbon atoms.

Examples of monovalent to hexavalent alcohols having 1 to 12 carbonatoms for the residue represented by Z include, as the monovalentalcohols: aliphatic monovalent alcohols such as methyl alcohol, ethylalcohol, n- or isopropyl alcohol, various butyl alcohols, various pentylalcohols, various hexyl alcohols, various octyl alcohols, various decylalcohols, and various dodecyl alcohols; alicyclic monovalent alcoholssuch as cyclopentyl alcohol and cyclohexyl alcohol; aromatic alcoholssuch as phenol, cresol, xylenol, butylphenol, and naphthol; and aromaticaliphatic alcohols such as benzyl alcohol and phenethyl alcohol; as thebivalent alcohols: aliphatic alcohols such as ethylene glycol, propyleneglycol, butylene glycol, neopentyl glycol, and tetramethylene glycol;alicyclic alcohols such as cyclohexanediol and cyclohexanedimethanol;and aromatic alcohols such as catechol, resorcinol, hydroquinone, anddihydroxy diphenyl; as trivalent alcohols: aliphatic alcohols such asglycerin, trimethylol propane, trimethylol ethane, trimethylol butane,and 1,3,5-pentatriol; alicyclic alcohols such as cyclohexanetriol andcyclohexanetrimethanol; and aromatic alcohols such as pyrogallol andmethylpyrogallol; and as tetravalent to hexavalent alcohols, aliphaticalcohols such as pentaerythritol, diglycerin, triglycerin, sorbitol, anddipentaerythritol.

Examples of the polycarbonate compound include compounds eachrepresented by the following general formula (XX-a) as a special form ofthe general formula (XX),

where R⁴⁰ represents a residue obtained by removing a hydroxyl groupfrom a monovalent alcohol having 1 to 12 carbon atoms, and R³⁵, R³⁶, c,and d each have the same meaning as that described above, and/orcompounds each represented by the following general formula (XXI-a) as aspecial form of the general formula (XXI),

where R³⁵, R³⁶, R³⁹, R⁴⁰, c, d, and g each have the same meaning as thatdescribed above.

Examples of the residue obtained by removing a hydroxyl group from amonovalent alcohol having 1 to 12 carbon atoms represented by R⁴⁰ ineach of the general formulae (XX-a) and (XXI-a) include: aliphatichydrocarbon groups such as a methyl group, an ethyl group, an n-propylgroup, an isopropyl group, various butyl groups, various pentyl groups,various hexyl groups, various octyl groups, various decyl groups, andvarious dodecyl groups; alicyclic hydrocarbon groups such as acyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, adimethylcyclohexyl group, and a decahydronaphthyl group; aromatichydrocarbon groups such as a phenyl group, various tolyl groups, variousxylyl groups, a mesityl group, and various naphthyl groups; and aromaticaliphatic hydrocarbon groups such as a benzyl group, a methylbenzylgroup, a phenethyl group, and various naphthylmethyl groups. Of those, astraight-chain or branched alkyl group having 1 to 6 carbon atoms ispreferable.

R³⁵, which represents a straight-chain or branched alkylene group having2 to 10 carbon atoms, preferably represents a straight-chain or branchedalkylene group having 2 to 6 carbon atoms, or particularly suitablyrepresents an ethylene group or a propylene group in terms of, forexample, the performance of the compound and the ease with which thecompound is produced. Further, R³⁶ represents a monovalent hydrocarbongroup having 1 to 12 carbon atoms or a group containing an ether bondrepresented by R³⁸ (O—R³⁷)_(f)— where R³⁸ represents a hydrogen atom ora monovalent hydrocarbon group having 1 to 12, or preferably 1 to 6carbon atoms, R³⁷ represents a straight-chain or branched alkylene grouphaving 2 to 10 carbon atoms, and f represents an integer of 1 to 20, andexamples of the above monovalent hydrocarbon group having 1 to 12 carbonatoms include examples similar to those described in the description ofR⁴⁰. In addition, a straight-chain or branched alkylene group having 2to 10 carbon atoms represented by R³⁷ is preferably a straight-chain orbranched alkylene group having 2 to 6 carbon atoms, or is particularlypreferably an ethylene group or a propylene group by the same reason asthat in the case of R³⁵.

R³⁶ particularly preferably represents a straight-chain or branchedalkyl group having 1 to 6 carbon atoms.

A straight-chain or branched alkylene group having 2 to 10 carbon atomsrepresented by R³⁹ in the general formula (XXI-a) is preferably astraight-chain or branched alkylene group having 2 to 6 carbon atoms, oris particularly preferably an ethylene group or a propylene group by thesame reason as that in the case of R³⁵.

Such a polycarbonate compound can be produced by any one of variousmethods; a target polycarbonate compound can be typically produced bycausing a carbonate-formable derivative such as a carbonic acid diesteror phosgene and an alkylene glycol or a polyalkylene glycol to reactwith each other in accordance with a known method.

In the present invention, one kind of those polycarbonates may be usedalone, or two or more kinds thereof may be used in combination.

In the refrigerator oil composition of the present invention, as a baseoil, a substance including, as a main component, at least one kind ofoxygen-containing compounds selected from the polyoxyalkylene glycols,polyvinyl ethers, copolymers of poly(oxy)alkylene glycols or monoethersthereof and polyvinyl ethers, polyol esters, and polycarbonates is used.Here, the phrase “including as a main component” refers to including theoxygen-containing compound at a rate of 50 mass % or more. The contentof the oxygen-containing compound in the base oil is preferably 70 mass% or more, more preferably 90 mass % or more, and still more preferably100 mass %.

In the present invention, the kinematic viscosity of the base oil at100° C. is preferably 2 to 50 mm²/s, more preferably 3 to 40 mm²/s, andstill more preferably 4 to 30 mm²/s. When the kinematic viscosity is 2mm²/s or more, favorable lubricity (load capacity resistance) isexhibited and sealing property is good, and when the kinematic viscosityis 50 mm²/s or less, energy saving is also favorable.

In addition, the number average molecular weight of the base oil ispreferably 500 or more, more preferably 600 to 3,000, and still morepreferably 700 to 2,500. The flashing point of the base oil ispreferably 150° C. or higher. When the number average molecular weightof the base oil is 500 or more, desirable performance as therefrigerator oil can be exhibited and the flashing point of the base oilcan be set to 150° C. or higher.

In the present invention, when the base oil has the above properties,the refrigerator oil composition may include, in addition to theoxygen-containing compound, another base oil at 50 mass % or less,preferably 30 mass % or less, and more preferably 10 mass % or less, andthe refrigerator oil composition free of another base oil is still morepreferred.

As the base oil that can be used together with the oxygen-containingcompound, other polyesters, a hydrogenation product of α-olefinoligomer,a mineral oil, an alicyclic hydrocarbon compound, an alkylated aromatichydrocarbon compound are exemplified.

At least one kind of an additive selected from an extreme pressureagent, an oiliness agent, an antioxidant, an acid scavenger, and ananti-foaming agent can be incorporated into the refrigerator oilcomposition of the present invention.

Examples of the extreme pressure agent include phosphorus-based extremepressure agents such as a phosphate, an acid phosphate, a phosphite, anacid phosphite, and amine salts thereof.

Of those phosphorus-based extreme pressure agents, tricresyl phosphate,trithiophenyl phosphate, tri(nonylphenyl) phosphite, dioleyl hydrogenphosphite, 2-ethylhexyldiphenyl phosphite, or the like is particularlypreferable in terms of extreme pressure property, a frictionalcharacteristic, and the like.

In addition, the examples of the extreme pressure agent include metalsalts of carboxylic acids. The term “metal salts of carboxylic acids” asused herein preferably refers to metal salts of carboxylic acids eachhaving 3 to 60 carbon atoms, and, further, aliphatic acids each having 3to 30, in particular, 12 to 30 carbon atoms. The examples furtherinclude metal salts of: dimer acids and trimer acids of the aliphaticacids; and dicarboxylic acids each having 3 to 30 carbon atoms. Ofthose, a metal salt of an aliphatic acid having 12 to 30 carbon atoms orof a dicarboxylic acid having 3 to 30 carbon atoms is particularlypreferred.

On the other hand, a metal of which any such metal salt is constitutedis preferably an alkali metal or an alkaline earth metal, and, inparticular, is optimally an alkali metal.

Further, examples of the extreme pressure agents and extreme pressureagents other than those mentioned above include sulfur type extremepressure agents such as sulfurized fat, sulfurized aliphatic acid,sulfurized ester, sulfurized olefin, dihydrocarvyl polysulphide,thiocarbamates, thioterpenes, and dialkyl thiodipropionates.

The blending amount of the above extreme pressure agent is in the rangeof preferably 0.001 to 5 mass % in ordinary cases, or particularlypreferably 0.005 to 3 mass % with reference to the total amount of thecomposition in terms of lubricity and stability.

One kind of the extreme pressure agents may be used alone, or two ormore kinds thereof may be used in combination.

Examples of the oiliness agents include, aliphatic saturated andunsaturated monocarboxylic acids such as stearic acid and oleic acid;polymerized aliphatic acids such as dimer acids and hydrogenated dimeracids; hydroxy aliphatic acids such as ricinoleic acid and12-hydroxystearic acid; aliphatic saturated and unsaturated monohydricalcohols such as lauryl alcohol and oleyl alcohol; aliphatic saturatedand unsaturated monoamines such as stearyl amine and oleylamine;aliphatic saturated and unsaturated monocarboxylic acid amides such aslauric acid amide and oleamide; and partial esters of a polyhydricalcohol such as glycerin and sorbitol, and an aliphatic saturated orunsaturated monocarboxylic acid.

One kind of the oiliness agents may be used alone, or two or more kindsthereof may be used in combination. In addition, the blending amount ofthe oiliness agent is selected from the range of typically 0.01 to 10mass %, or preferably 0.1 to 5 mass % with reference to the total amountof the composition.

A phenol-based antioxidant such as 2,6-di-tert-butyl-4-methylphenol,2,6-di-tert-butyl-4-ethylphenol, or2,2′-methylenebis(4-methyl-6-tert-butylphenol) or an amine-basedantioxidant such as phenyl-α-naphthylamine orN,N′-di-phenyl-p-phenylenediamine is preferably blended as theantioxidant. The antioxidant is blended in the composition at a contentof typically 0.01 to 5 mass %, or preferably 0.05 to 3 mass % in termsof an effect, economical efficiency, and the like.

Examples of the acid scavenger include: phenyl glycidyl ether; alkylglycidyl ether; alkylene glycol glycidyl ether; cyclohexeneoxide;α-olefinoxide; and an epoxy compound such as epoxidized soybean oil. Ofthose, phenyl glycidyl ether, alkyl glycidyl ether, alkylene glycolglycidyl ether, cyclohexeneoxide, or α-olefinoxide is preferable interms of compatibility with the refrigerant.

Each of an alkyl group of the alkyl glycidyl ether and an alkylene groupof the alkylene glycol glycidyl ether may be branched, and has typically3 to 30, preferably 4 to 24, or particularly preferably 6 to 16 carbonatoms. In addition, one having a total of generally 4 to 50, preferably4 to 24, or particularly preferably 6 to 16 carbon atoms is used as theα-olefinoxide. In the present invention, one kind of the acid scavengersmay be used, or two or more kinds thereof may be used in combination. Inaddition, the blending amount of the acid scavenger is in the range ofpreferably 0.005 to 5 mass % in ordinary cases, or particularlypreferably 0.05 to 3 mass % with reference to the composition in termsof an effect and the suppression of the generation of sludge.

In the present invention, the stability of the refrigerator oilcomposition can be improved by blending the acid scavenger. The combineduse of the extreme pressure agent and the antioxidant with the acidscavenger exerts an additional improving effect on the stability.

As the antifoaming agent, a silicone oil, a fluorinated silicone oil,and the like are exemplified.

In the refrigerator oil composition of the present invention, anotherknown various additives, for example, a copper inactivator such asN—[N,N′-dialkyl (alkyl group having 3 to 12 carbon atoms)aminomethyl]triazole may be blended appropriately in the range of theblending amount which does not inhibit the purpose of the presentinvention.

The refrigerator oil composition of the present invention is applied toa refrigerator employing a refrigerant including at least one kind offluorine-containing organic compounds selected from the compoundsrepresented by the molecular formula (A) or a combination of thefluorine-containing organic compound and a saturated fluorinatedhydrocarbon compound.

In addition, the refrigerator oil composition of the present inventionis applied to a refrigerator employing a refrigerant including at leastone kind of fluorine-containing organic compounds selected fromfluorinated ether compounds, fluorinated alcohol compounds, andfluorinated ketone compounds, or a combination of thefluorine-containing organic compound and a saturated fluorinatedhydrocarbon compound.

The used amounts of any one of the various refrigerants and therefrigerator oil composition in a method of lubricating a refrigeratorthat uses the refrigerator oil composition of the present invention aresuch that a mass ratio of the refrigerant to the refrigerator oilcomposition is in the range of preferably 99/1 to 10/90, or morepreferably 95/5 to 30/70. The amount of the refrigerant below the aboverange is not preferable because a reduction in refrigerating capacity ofthe refrigerator is observed. In addition, the amount of the refrigerantbeyond the above range is not preferable because the lubricity of thecomposition reduces. The refrigerator oil composition of the presentinvention, which can be used in any one of various refrigerators, isparticularly preferably applicable to the compression refrigeratingcycle of a compression refrigerator.

The refrigerator to which the refrigerator oil composition of thepresent invention is applied has a refrigerating cycle which essentiallyneeds a constitute of a compressor, a condenser, an expansion mechanism(such as an expansion valve), and an evaporator, or a compressor, acondenser, an expansion mechanism, a drier, and an evaporator, uses theabove-mentioned refrigerator oil composition of the present invention asa refrigerator oil, and uses the above-mentioned various refrigerants asrefrigerants.

Here, the drier is preferably filled with a desiccant formed of zeolitehaving a pore diameter of 0.33 nm or less. In addition, as the zeolite,a natural zeolite or a synthetic zeolite may be exemplified. Zeolitehaving a CO₂ gas absorbing amount of 1.0% or less at 25° C. and a CO₂gas partial pressure of 33 kPA is more suitable. As the syntheticzeolite described above, XH-9 (trade name), XH-600 (trade name)manufactured by UNION SHOWA K. K., and the like are exemplified.

In the present invention, if the desiccant is used, moisture can beremoved efficiently without absorbing of the refrigerant in therefrigerating cycle, and simultaneously, powderization of the desiccantdue to deterioration of the desiccant itself is suppressed. Therefore,there is no possibility of clogging of pipes caused by the powderizationor abnormal wear caused by entering of the powder into a sliding part ofthe compressor, whereby the refrigerator can be driven stably for a longtime period.

Various sliding parts (such as a bearing) are present in a compressor ina refrigerator to which the refrigerator oil composition of the presentinvention is applied. In the present invention, a part composed ofengineering plastic, or a part having an organic or inorganic coatingfilm is used as each of the sliding parts in terms of, in particular,sealing property.

Preferable examples of the engineering plastic include a polyamideresin, a polyphenylene sulfide resin, and a polyacetal resin in terms ofsealing property, sliding property, wear resistance, and the like.

In addition, examples of the organic coating film include afluorine-containing resin coating film (such as apolytetrafluoroethylene coating film), a polyimide coating film, and apolyamideimide coating film in terms of sealing property, slidingproperty, wear resistance, and the like.

On the other hand, examples of the inorganic coating film include agraphite film, a diamond-like carbon film, a nickel film, a molybdenumfilm, a tin film, and a chromium film in terms of sealing property,sliding property, wear resistance, and the like. The inorganic coatingfilm may be formed by a plating treatment, or may be formed by aphysical vapor deposition method (PVD).

It should be noted that a part composed of, for example, a conventionalalloy system such as an Fe base alloy, an Al base alloy, or a Cu basealloy can also be used as each of the sliding parts.

The refrigerator oil composition of the present invention can be used ineach of a car air conditioner, an electrically-driven air conditioner, agas heat pump, an air conditioner, a cold storage, various hot watersupply systems such as a vending machine or a showcase, and arefrigerating and heating system.

In the present invention, the water content in the system is preferably300 mass ppm or less and more preferably 200 mass ppm or less. Inaddition, the residual air amount in the system is preferably 10 kPa orless and more preferably 5 kPa or less.

The refrigerator oil composition of the present invention mainlyincludes a specific oxygen-containing compound as a base oil, has so lowviscosity that energy saving can be improved, and has excellent sealingproperty.

EXAMPLES

Next, the present invention is described in more detail by way ofexamples. However, the present invention is by no means limited by thoseexamples.

It should be noted that properties of the base oil and variouscharacteristics of the refrigerator oil composition were determinedaccording to the following procedure.

<Properties of Base Oil>

(1) Kinematic Viscosity at 100° C.

The kinematic viscosity at 100° C. was measured according to JISK2283-1983 by using a glass capillary viscometer.

(2) Flashing Point

The flashing point was measured according to JIS K2265 by C.O.C method.

(3) Number Average Molecular Weight

The number average molecular weight was measured by gel permeationchromatography (GPC).

<Various Characteristics of Refrigerator Oil Composition>

(4) Two-Layer Separation Temperature

A measuring tube for two-layer separation temperature (internal volume:10 mL) was filled with water (0.6 g) and a refrigerant (2.4 g) and keptin a thermostatic chamber. The temperature in the thermostatic chamberwas increased from room temperature (25° C.) at a rate of 1° C./min,whereby a two-layer separation temperature was measured.

(5) Stability (Sealed Tube Test)

A glass tube was filled with an oil (4 mL) and a refrigerant (1 g, watercontent of 200 ppm), and metal catalysts of iron, copper, and aluminum,and sealed. After the glass tube was kept at an air pressure of 26.6 kPaand at a temperature of 175° C. for 10 days, oil appearance, catalystappearance, and the presence or absence of sludge were visually observedand the acid value was measured.

In addition, the kinds of components used in preparation of therefrigerator oil composition are described below.

(1) Base Oil

A1: polypropylene glycol dimethyl ether having a kinematic viscosity of9.25 mm²/s at 100° C., a flashing point of 212° C., and a number averagemolecular weight of 1,139

A2: polypropylene glycol (PPG)/polyethylene glycol (PEG) dimethyl ether(PPG/PEG molar ratio of 9/1) having a kinematic viscosity of 10.34 mm²/sat 100° C., a flashing point of 223° C., and a number average molecularweight of 1,116

A3: polypropylene glycol/polyethylene glycol dimethyl ether (PPG/PEGmolar ratio of 8/2) having a kinematic viscosity of 20.05 mm²/s at 100°C., a flashing point of 230° C., and a number average molecular weightof 1,730

A4: polypropylene glycol methylnonylphenyl ether having a kinematicviscosity of 11.76 mm²/s at 100° C., a flashing point of 220° C., and anumber average molecular weight of 1,100

A5: polypropylene glycol dioctyl ether having a kinematic viscosity of11.31 mm²/s at 100° C., a flashing point of 219° C., and a numberaverage molecular weight of 1,090

A6: polyethyl vinyl ether having a kinematic viscosity of 15.97 mm²/s at100° C., a flashing point of 222° C., and a number average molecularweight of 1,250

A7: a copolymer of polyethyl vinyl ether (PEV)/polyisobutyl vinyl ether(PIBV) (PEV/PIBV molar ratio of 9/1) having a kinematic viscosity of8.26 mm²/s at 100° C., a flashing point of 206° C., and a number averagemolecular weight of 830

A8: a copolymer of polypropylene glycol (PPG)/polyethyl vinyl ether(PEV) (PPG/PEV molar ratio of 7/11) having a kinematic viscosity of 9.56mm²/s at 100° C., a flashing point of 218° C., and a number averagemolecular weight of 1,200

A9: a copolymer of polyethylene glycol (PEG)/polyethyl vinyl ether (PEV)(PEG/PEV molar ratio of 3/21) having a kinematic viscosity of 17.64mm²/s at 100° C., a flashing point of 232° C., and a number averagemolecular weight of 1,680

A10: a copolymer of polypropylene glycol (PPG)/polyethyl vinyl ether(PEV) (PPG/PEV molar ratio of 16/5) having a kinematic viscosity of13.49 mm²/s at 100° C., a flashing point of 223° C., and a numberaverage molecular weight of 1,280

A11: pentaerythritol octanoic acid (C8 acid) nonanoic acid (C9 acid)ester (C8 acid/C9 acid molar ratio of 1/1.1) having a kinematicviscosity of 9.64 mm²/s at 100° C., a flashing point of 268° C., and anumber average molecular weight of 670

A12: pentaerythritol octanoic acid nonanoic acid ester (C8 acid/C9 acidmolar ratio of 1/1.7) having a kinematic viscosity of 15.99 mm²/s at100° C., a flashing point of 289° C., and a number average molecularweight of 685

A13: paraffin-based mineral oil having a kinematic viscosity of 10.68mm²/s at 100° C. and a flashing point of 266° C.

A14: alkyl benzene having a kinematic viscosity of 5.85 mm²/s at 100° C.and a flashing point of 196° C.

(2) Additive

Extreme-pressure agent B1: tricresyl phosphate

Acid scavenger B2: C14 α-olefin oxide

Antioxidant B3: 2,6-di-t-butyl-4-methyl phenol

Antifoaming agent B4: silicone-based antifoaming agent

In addition, the kinds of the used refrigerants are described below.

Ref1-1: 1,1,1-trifluorodimethyl ether

Ref1-2: 1,1,2-trifluorodimethyl ether

Ref1-3: 1,1,1,2-tetrafluorodimethyl ether

Ref1-4: 1,1,2,2-tetrafluorodimethyl ether

Ref1-5: a mixture of Ref1-2 and Ref1-4 (mass ratio of 1/1)

Ref2-1: trifluoromethyl alcohol

Ref2-2: difluoromethyl alcohol

Ref2-3: monofluoromethyl alcohol

Ref2-4: 1,1,1-trifluoroethyl alcohol

Ref2-5: 1,1,2-trifluoroethyl alcohol

Ref3-1: 1,1-difluoroacetone

Ref3-2: 1,1,1-trifluoroacetone

Ref3-3: 1,1,2-trifluoroacetone

Ref3-4: 1,1,1,2-tetrafluoroacetone

Ref3-5: a mixture of Ref3-1 and Ref3-3 (mass ratio of 1/1)

Examples 1 to 12 and Comparative Examples 1 and 2

Refrigerator oil compositions having the compositions shown in Table 1were prepared. Ref1-1, Ref1-2, Ref1-3, Ref1-4, and Ref1-5, each of whichwas a refrigerant formed of a fluorinated ether compound shown in Table1, were used, and characteristics of the compositions were evaluated.Table 1 shows the results.

TABLE 1 Example 1 2 3 4 5 6 7 Blending Base oil Kind A1 A2 A3 A4 A5 A6A7 composition (Mass %) 97.5  97.5   97.499  97.499 97.5  97.5  97.5 Additive (mass %) Extreme pressure agent B1 1.0 1.0 1.0 1.0 1.0 1.0 1.0Acid scavenger B2 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Antioxidant B3 0.5 0.5 0.50.5 0.5 0.5 0.5 Antifoaming agent B4 — —  0.001  0.001 — — —Characteristics Two-layer Kind of Ref1-1 40<   40<   40<   40<   40<  40<   40<   separation refrigerant Ref1-2 40<   40<   40<   40<   40<  40<   40<   temperature (° C.) Ref1-3 40<   40<   40<   40<   40<  40<   40<   [oil content: 20 Ref1-4 40<   40<   40<   40<   40<   40<  40<   mass %] Ref1-5 40<   40<   40<   40<   40<   40<   40<   Sealedtube test Oil appearance Good Good Good Good Good Good Good Catalystappearance Good Good Good Good Good Good Good Presence or absence ofsludge Absent Absent Absent Absent Absent Absent Absent Acid value(mgKOH/g)  0.01>  0.01>  0.01>  0.01>  0.01>  0.01>  0.01> ExampleComparative Example 8 9 10 11 12 1 2 Blending Base oil Kind A8 A9 A10A11 A12 A13 A14 composition (Mass %) 97.5  97.5  97.5  97.5  97.5  97.5 97.5  Additive Extreme pressure agent B1 1.0 1.0 1.0 1.0 1.0 1.0 1.0(mass %) Acid scavenger B2 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Antioxidant B30.5 0.5 0.5 0.5 0.5 0.5 0.5 Antifoaming agent B4 — — — — — — —Characteristics Two-layer Kind of Ref1-1 40<   40<   40<   40<   40<  separated at separated at separation refrigerant room room temperaturetemperature temperature (° C.) [oil Ref1-2 40<   40<   40<   40<   40<  separated at separated at content: 20 room room mass %] temperaturetemperature Ref1-3 40<   40<   40<   40<   40<   separated at separatedat room room temperature temperature Ref1-4 40<   40<   40<   40<  40<   separated at separated at room room temperature temperature Ref1-540<   40<   40<   40<   40<   separated at separated at room roomtemperature temperature Sealed tube Oil appearance Good Good Good GoodGood — — test Catalyst appearance Good Good Good Good Good — — Presenceor absence of sludge Absent Absent Absent Absent Absent — — Acid value(mgKOH/g)  0.01>  0.01>  0.01>  0.01>  0.01> — — (Note) Sealed tubetest: Ref1-1 was used as a refrigerant.

As understood from Table 1, the refrigerator oil compositions (Examples1 to 12) of the present invention have the two-layer separationtemperature exceeding 40° C. with respect to all kinds of refrigerantsRef1-1 to Ref1-5 and have excellent stability in the sealed tube testusing Ref1-1. On the contrary, in Comparative Examples 1 and 2, therefrigerator oil compositions are separated at room temperature withrespect to all refrigerants Ref1-1 to Ref1-5.

Examples 13 to 24 and Comparative Examples 3 and 4

Refrigerator oil compositions having the compositions shown in Table 2were prepared. Ref2-1, Ref2-2, Ref2-3, Ref2-4, and Ref2-5, each of whichwas a refrigerant formed of a fluorinated alcohol compound shown inTable 2, were used, and characteristics of the compositions wereevaluated. Table 2 shows the results.

TABLE 2 Example 13 14 15 16 17 18 19 Blending Base oil Kind A1 A2 A3 A4A5 A6 A7 composition (Mass %) 97.5  97.5   97.499  97.499 97.5  97.5 97.5  Additive (mass %) Extreme pressure agent B1 1.0 1.0 1.0 1.0 1.01.0 1.0 Acid scavenger B2 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Antioxidant B3 0.50.5 0.5 0.5 0.5 0.5 0.5 Antifoaming agent B4 — —  0.001  0.001 — — —Characteristics Two-layer Kind of Ref2-1 40<   40<   40<   40<   40<  40<   40<   separation refrigerant Ref2-2 40<   40<   40<   40<   40<  40<   40<   temperature (° C.) Ref2-3 40<   40<   40<   40<   40<  40<   40<   [oil content: 20 Ref2-4 40<   40<   40<   40<   40<   40<  40<   mass %] Ref2-5 40<   40<   40<   40<   40<   40<   40<   Sealedtube test Oil appearance Good Good Good Good Good Good Good Catalystappearance Good Good Good Good Good Good Good Presence or absence ofsludge Absent Absent Absent Absent Absent Absent Absent Acid value(mgKOH/g)  0.01>  0.01>  0.01>  0.01>  0.01>  0.01>  0.01> ExampleComparative Example 20 21 22 23 24 3 4 Blending Base oil Kind A8 A9 A10A11 A12 A13 A14 composition (Mass %) 97.5  97.5  97.5  97.5  97.5  97.5 97.5  Additive Extreme pressure agent B1 1.0 1.0 1.0 1.0 1.0 1.0 1.0(mass %) Acid scavenger B2 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Antioxidant B30.5 0.5 0.5 0.5 0.5 0.5 0.5 Antifoaming agent B4 — — — — — — —Characteristics Two-layer Kind of Ref2-1 40<   40<   40<   40<   40<  separated at separated at separation refrigerant room room temperaturetemperature temperature (° C.) [oil Ref2-2 40<   40<   40<   40<   40<  separated at separated at content: 20 room room mass %] temperaturetemperature Ref2-3 40<   40<   40<   40<   40<   separated at separatedat room room temperature temperature Ref2-4 40<   40<   40<   40<  40<   separated at separated at room room temperature temperature Ref2-540<   40<   40<   40<   40<   separated at separated at room roomtemperature temperature Sealed tube Oil appearance Good Good Good GoodGood — — test Catalyst appearance Good Good Good Good Good — — Presenceor absence of sludge Absent Absent Absent Absent Absent — — Acid value(mgKOH/g)  0.01>  0.01>  0.01>  0.01>  0.01> — — (Note) Sealed tubetest: Ref2-1 was used as a refrigerant.

As understood from Table 2, the refrigerator oil compositions (Examples13 to 24) of the present invention have the two-layer separationtemperature exceeding 40° C. with respect to all kinds of refrigerantsRef2-1 to Ref2-5 and have excellent stability in the sealed tube testusing Ref2-1. On the contrary, in Comparative Examples 3 and 4, therefrigerator oil compositions are separated at room temperature withrespect to all refrigerants Ref2-1 to Ref2-5.

Examples 25 to 36 and Comparative Examples 5 and 6

Refrigerator oil compositions having the compositions shown in Table 3were prepared. Ref3-1, Ref3-2, Ref3-3, Ref3-4, and Ref3-5, each of whichwas a refrigerant formed of a fluorinated ketone compound shown in Table3, were used, and characteristics of the compositions were evaluated.Table 3 shows the results.

TABLE 3 Example 25 26 27 28 29 30 31 Blending Base oil Kind A1 A2 A3 A4A5 A6 A7 composition (Mass %) 97.5  97.5   97.499  97.499 97.5  97.5 97.5  Additive (mass %) Extreme pressure agent B1 1.0 1.0 1.0 1.0 1.01.0 1.0 Acid scavenger B2 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Antioxidant B3 0.50.5 0.5 0.5 0.5 0.5 0.5 Antifoaming agent B4 — —  0.001  0.001 — — —Characteristics Two-layer Kind of Ref3-1 40<   40<   40<   40<   40<  40<   40<   separation refrigerant Ref3-2 40<   40<   40<   40<   40<  40<   40<   temperature (° C.) Ref3-3 40<   40<   40<   40<   40<  40<   40<   [oil content: 20 Ref3-4 40<   40<   40<   40<   40<   40<  40<   mass %] Ref3-5 40<   40<   40<   40<   40<   40<   40<   Sealedtube test Oil appearance Good Good Good Good Good Good Good Catalystappearance Good Good Good Good Good Good Good Presence or absence ofsludge Absent Absent Absent Absent Absent Absent Absent Acid value 0.01>  0.01>  0.01>  0.01>  0.01>  0.01>  0.01> (mgKOH/g) ExampleComparative Example 32 33 34 35 36 5 6 Blending Base oil Kind A8 A9 A10A11 A12 A13 A14 composition (Mass %) 97.5  97.5  97.5  97.5  97.5  97.5 97.5  Additive Extreme pressure agent B1 1.0 1.0 1.0 1.0 1.0 1.0 1.0(mass %) Acid scavenger B2 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Antioxidant B30.5 0.5 0.5 0.5 0.5 0.5 0.5 Antifoaming agent B4 — — — — — — —Characteristics Two-layer Kind of Ref3-1 40<   40<   40<   40<   40<  separated at separated at separation refrigerant room room temperaturetemperature temperature (° C.) [oil Ref3-2 40<   40<   40<   40<   40<  separated at separated at content: 20 room room mass %] temperaturetemperature Ref3-3 40<   40<   40<   40<   40<   separated at separatedat room room temperature temperature Ref3-4 40<   40<   40<   40<  40<   separated at separated at room room temperature temperature Ref3-540<   40<   40<   40<   40<   separated at separated at room roomtemperature temperature Sealed tube Oil appearance Good Good Good GoodGood — — test Catalyst appearance Good Good Good Good Good — — Presenceor absence of sludge Absent Absent Absent Absent Absent — — Acid value(mgKOH/g)  0.01>  0.01>  0.01>  0.01>  0.01> — — (Note) Sealed tubetest: Ref3-2 was used as a refrigerant.

As understood from Table 3, the refrigerator oil compositions (Examples25 to 36) of the present invention have the two-layer separationtemperature exceeding 40° C. with respect to all kinds of refrigerantsRef3-1 to Ref3-5 and have excellent stability in the sealed tube testusing Ref3-2. On the contrary, in Comparative Examples 5 and 6, therefrigerator oil compositions are separated at room temperature withrespect to all refrigerants Ref3-1 to Ref3-5.

INDUSTRIAL APPLICABILITY

The lubricating oil composition for a refrigerator of the presentinvention is used for a refrigerator that uses, as a refrigerant, afluorine-containing organic compound which is a refrigerant applicableto, in particular, current car air conditioner systems or the like, hasa specific polar structure and has a low global warming potential.

The invention claimed is:
 1. A composition, comprising: (i) arefrigerant consisting of an unsaturated fluorinated hydrocarboncompound represented by formula (A):C_(p)O_(q)F_(r)R_(s)  (A) wherein R represents H; p represents aninteger from 2 to 6, q is 0, r represents an integer from 1 to 12, and srepresents an integer from 0 to 11, and the compound contains one ormore unsaturated carbon-carbon bonds; and (ii) a lubricating oilcomposition for a refrigerator comprising a base oil containing at leastone polyol ester as a main component, wherein the polyol ester is anester of (1) at least one diol or polyol selected from the groupconsisting of neopentyl glycol, trimethylolethane, trimethylolpropane,trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane),pentaerythritol, di-(pentaerythritol) and tri-(pentaerythritol), and (2)an aliphatic acid having 3 to 18 carbon atoms.
 2. The compositionaccording to claim 1, wherein the unsaturated refrigerant fluorinatedhydrocarbon compound is a fluorinated propene compound.
 3. Thecomposition according to claim 2, wherein the fluorinated propenecompound is an isomer of pentafluoropropene, 3,3,3-trifluoropropene or1,3,3,3-tetrafluoropropene.
 4. The composition according to claim 1,wherein the aliphatic acid has 3 to 12 carbon atoms.
 5. The compositionaccording to claim 1, wherein the aliphatic acid has 5 to 9 carbonatoms.
 6. The composition according to claim 1, wherein the aliphaticacid used for obtaining the polyol esters is a branched aliphatic acid.7. The composition according to claim 1, wherein the polyol comprises atleast one member selected from the group consisting of neopentyl glycol,trimethylolethane, trimethylolpropane, trimethylolbutane andpentaerythritol.
 8. The composition according to claim 1, wherein thepolyol comprises pentaerythritol.
 9. The composition according to claim1, wherein the polyol ester is an ester formed of two or more kinds ofmixed aliphatic acids and a polyol.
 10. The composition according toclaim 1, wherein the base oil has a kinematic viscosity of 2 to 50 mm²/sat 100° C.
 11. The composition according to claim 1, wherein the baseoil has a flash point of 150° C. or higher.
 12. The compositionaccording to claim 1, further comprising at least one additive selectedfrom the group consisting of an extreme pressure agent, an oilinessagent, an antioxidant, an acid scavenger and an anti-foaming agent. 13.A car air conditioner, an electrically-driven car air conditioner, a gasheat pump, an air conditioner, a cold storage, a hot-water supply systemfor a vending machine or a showcase, or a refrigerating and heatingsystem, comprising the composition of claim
 1. 14. The car airconditioner, an electrically-driven car air conditioner, a gas heatpump, an air conditioner, a cold storage, a hot-water supply system fora vending machine or a showcase, or a refrigerating and heating systemaccording to claim 13, wherein a water content in a system is 300 massppm or less and a residual air content is 10 kPa or less.
 15. A methodof lubricating a refrigerator comprising incorporating into therefrigerator a composition comprising: (i) a refrigerant consisting ofan unsaturated fluorinated hydrocarbon compound represented by formula(A):C_(p)O_(q)F_(r)R_(s)  (A) wherein R represents H; p represents aninteger from 2 to 6, q is 0, r represents an integer from 1 to 12, and srepresents an integer from 0 to 11, and the compound contains one ormore unsaturated carbon-carbon bonds; and (ii) a lubricating oilcomposition for a refrigerator comprising a base oil containing at leastone polyol ester as a main component, wherein the polyol ester is anester of (1) at least one diol or polyol selected from the groupconsisting of neopentyl glycol, trimethylolethane, trimethylolpropane,trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane),pentaerythritol, di-(pentaerythritol) and tri-(pentaerythritol), and (2)an aliphatic acid having 3 to 18 carbon atoms.
 16. A refrigerator whichcomprises a compressor, a condenser, an expansion mechanism and anevaporator and which contains a composition comprising: (i) arefrigerant consisting of an unsaturated fluorinated hydrocarboncompound represented by formula (A):C_(p)O_(q)F_(r)R_(s)  (A) wherein R represents H; p represents aninteger from 2 to 6, q is 0, r represents an integer from 1 to 12, and srepresents an integer from 0 to 11, and the compound contains one ormore unsaturated carbon-carbon bonds; and (ii) a lubricating oilcomposition for a refrigerator comprising a base oil containing at leastone polyol ester as a main component, wherein the polyol ester is anester of (1) at least one diol or polyol selected from the groupconsisting of neopentyl glycol, trimethylolethane, trimethylolpropane,trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane),pentaerythritol, di-(pentaerythritol) and tri-(pentaerythritol), and (2)an aliphatic acid having 3 to 18 carbon atoms.
 17. The compositionaccording to claim 1, wherein the unsaturated refrigerant fluorinatedhydrocarbon compound is 3,3,3-trifluoropropene.
 18. The compositionaccording to claim 1, wherein the base oil consists of at least onepolyol ester, wherein the polyol ester is an ester of (1) at least onediol or polyol is selected from the group consisting of neopentylglycol, trimethylolethane, trimethylolpropane, trimethylolbutane,di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol,di-(pentaerythritol) and tri-(pentaerythritol), and (2) an aliphaticacid having 3 to 18 carbon atoms.
 19. The composition according to claim18, wherein the polyol ester is an ester formed of two or more kinds ofmixed aliphatic acids and a polyol.